This invention relates to apparatus for expanding data that has geen compacted. More particularly, the invention relates to apparatus for data expansion which is particularly useful in systems wherein long data sections of varying lengths are repetitively used varying numbers of times.
In systems such as the one described in U.S. Pat. No. 3,644,700 for "Method And Apparatus For Controlling An Electron Beam" by R. V. Kruppa, long sections of the same data are repetitively used over and over again. The data used to control an electron beam are typically stored initially on a magnetic disk, from which they are read into in a memory buffer. From the buffer they are again read out and used for control of the beam. In a typical prior art system such as the one shown in the patent, beam control data are read from a disk into the buffer, these data are used for beam control, and then the next block of beam control data is read from the disk into the buffer. The amount of time that is taken for reading data from the disk into the buffer is a significant throughout limiting factor. Also, a significant amount of space on the disks can be required to hold all of the pattern data.